Extend TextEditorLineNumbersStyle with Interval

[pyrrho]

• Extend TextEditorLineNumbersStyle in both extHostTypes.ts and vscode.d.ts with an Interval member.
• Update extHostTypeConverters.ts to convert between TextEditorLineNumbersStyle.Interval and (the already extant) RenderLineNumbersType.Interval.
• Update MainThreadTextEditor.setConfiguration to handle { ..., lineNumbers: 'interval' }.

This should allow extensions to read from/write to vscode.window.activeTextEditor.options.lineNumbers to detect and apply the Interval configuration. This PR was tested by starting a debugging session, and modifying the above field in the Debug Console.

This PR may be relevant to #85471, though that issue is closed, and was locked in January of 2022. (It says there are three comments on there, but I'm not seeing them. I'm guessing they added after the github-actions bot locked the issue and community members can't access them?)

I'd be happy to open a new issue to link this PR to if that would be helpful to the process.

[pyrrho]

@microsoft-github-policy-service agree

[rebornix]

@hediet the code looks reasonable to me, I'll leave it to you to decide if we want to take the API change in.